Mobile phones, and other small computing devices, are being built with increasingly large display surfaces. While the devices themselves, in general, are smaller than they were several years ago, modern devices devote a relatively larger percentage of the device's surface to the display. Early devices typically had a mechanical keypad for input and a screen to display output. Since the keypad and screen coexisted on the same side of the device, there was a limit as to how large the display could be. While some phones continue to use mechanical keypads (which are favored by some users), advances in touch-screen technology have allowed other devices to omit the keypad entirely in favor of a touch-screen interface that acts as both an input device and a display. This design allows a larger portion of the surface area to be used as a display.
Some devices include more than one display area. For example, some phones with a “flip” or “slide out” design include plural displays—e.g., one large display as the main viewing area, and another smaller display to show a clock, a “message waiting” indicator, etc. In some cases, one of the displays may use less power per viewing area than the other display—e.g., one display may be color and the other may be monochrome (where a monochrome display generally uses less power than a color display).
Despite these designs, phones and other devices generally include less display real estate than they could. There is often a considerable amount of surface area on the device that could accommodate a display, but that is not being used as a display.